The present invention relates to trailer hitches, and particularly to hitches which allow movement of the hitching point, such as fore and aft adjustability of a fifth wheel hitch. Hitches have long been used to attach a towed load, such as a trailer, to a towing vehicle such as a tractor or a truck. Most hitches permit the towed load to pivot in its orientation relative to the towing vehicle about a generally vertical axis, such as when the towing vehicle turns a corner. For some hitches, the hitching point which establishes the pivot axis of the hitch is a ball supported on the towing vehicle. For other hitches such as fifth wheel hitches, the hitching point which establishes the pivot axis is a kingpin extending from the towed load. In either situation, large forces are frequently transmitted through the hitching point, not only pulling rearwardly due to the drag of the towed load during towing, but also forward, up, down and sideways during slowing or stopping, towing up and down hills, traveling on sideslopes or around corners, traversing over bumpy roads, etc.
For many applications, the hitching point can be fixed relative to the towing vehicle, and never change. For other applications, adjustment of the location of the hitching point relative to the towing vehicle occurs infrequently, such that a mechanical repositioning by hand is appropriate. For example, many hitches have two or more sets of mounting holes, so as to be adjustable in their position by changing the set of mounting holes used with the mounting bolts. For some applications, however, frequent and easy changing of the location of the hitching point is desirable, and particularly laterally moving the hitching point (i.e., moving the hitching point forward, backward, to the left, or to the right on the hitching vehicle.) A common use of such lateral movement is to enable tighter turning during parking (i.e., providing greater clearance between the trailer and the cab of the towing vehicle), and then repositioning the hitching point for towing at highway speeds. The present invention is particularly directed at enabling such lateral movement of the hitching point of a hitch.
The hitch must be strong to securely engage the trailer, minimizing the possibility of breakage or of any way the trailer could inadvertently come loose. At the same time, the hitch should be simple to operate, so the operator has no difficulty in intentionally moving the location of the hitching point. Operation of the controls should not require the application of excessive force or torque. The average operator of a fifth-wheel or gooseneck hitch is not young, such as over 55 years old, who is perhaps not as strong and nimble as he or she once was. The controls of the hitch should be readily accessible by the operator, without requiring too much climbing or bending to access. The hitch should preferably be mechanically operated, so there is no possibility of a loss of power preventing operation of the hitch.
Towing conditions are such that hitches are normally subjected to considerable amounts of dirt and grime, and treated very roughly. The hitch should readily withstand such conditions. The hitch must be robust and reliable, to last for carefree operation over the life of at least one vehicle, and possibly over the life of several vehicles, despite the fact that the hitch will likely be openly exposed to weather over its years or decades of use. As much as possible, the hitch should also have minimal cost and expense in manufacturing and assembly. In keeping with these objectives, further improvements to hitch designs permitting lateral movement of the hitching point are possible.